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UNIVERSITY  OF  ILLINOIS 

Agricultural  Experiment  Station 


BULLETIN  No.  163 


THE  MAINTENANCE  REQUIREMENT 
OF   SWINE 


BY  WILLIAM    DIETRICH 


URBANA,  ILLINOIS,  JUNE,  1913 


SUMMARY  OF  BULLETIN  No.    163 

1.  OBJECT. — To  determine  the  amounts  of  feed   required   for  the  mainte- 
nance of  swine  under  different  conditions.     The   maintenance    ration   may  be 
defined  as  one  containing  enough  of  the  various  nutrients    (protein,  carbohy- 
drate, ether  extract,  mineral  matter,  and  water)  to  support  the  animal  without 
the  production  of  growth  or  of  work. 

2.  PLAN. — Pigs  differing  in  age,  breeding,  and  conformation  were  used  in 
three  successive  experiments,  including  twenty-six  separate  maintenance  periods, 
to  determine  the  amount  of  feed  and  of  the  respective  nutrients  required  for 
maintenance.     The  rations  were  gradually  reduced  during  several  weeks'  time 
until    quantities    were    reached   that   maintained    a   constant   live    weight.    'The 
coefficients  of   digestibility  of  the  various  nutrients  were  determined   in  most 
instances.     In  the  last  experiment,  the  nitrogen  balance  "and   the  consumption 
and  excretion  of  water  also  were  determined  to  show  whether  the  live  weight 
was  maintained  by  the  substitution  of  water  for  body  tissue. 

3.  ANIMALS  USED. — In  the  first  experiment  four  pigs  of  mixed  breeding. 
were  used  in  four  separate  periods  at  50,  100,  150,  and  200  pounds  live  weight, 
respectively.     In    the   second   experiment,    three   pigs   were   used :    a    Berkshire 
3  years  old,  a   Poland-China   \l/2  years   old,   and  a   Poland-China   1  .year  old. 
In   the   third    experiment,    two  yearling    Berkshire   barrows    were    used   which 
weighed  240  and  320  pounds  respectively. 

4.  RATIONS  FED. — In  Experiment  No.  1,  the  feed  consisted  of  ground  corn, 
wheat  middlings,   and  skim  milk ;    in  Experiment  No.  2,  ground  corn,  wheat, 
bran,  wheat  middlings  and  tankage ;  and  in  Experiment  No.  3,  ground  rorn,  red 
dog  flour,  tankage,  and  pork  cracklings.     The  latter  experiment  also  included  a 
fasting  period  of  eight  days. 

5.  EXPERIMENT  No.  1. — The  apparent  maintenance  requirement  per  day  per 
100  pounds  live  weight  of  the  50-pound  pigs  was  0.121  pounds  crude  protein,  0.434 
pound   carbohydrate,   0.02   pound    ether   extract;    of   the   100-pound   pigs,    0.124 
pound  protein,  0.517  pound  carbohydrate,  0.026  pound  ether  extract;  of  the  150- 
pound  pigs,  0.131  pound  protein,  0.633   pound  carbohydrate,  0.033  pound  ether 
extract;  of  the  200-pound  pigs,  0.102  pound  protein,  0.549  pound  carbohydrate, 
and  0.033  pound  ether  extract.  Page  417 

6.  EXPERIMENT  No.  2. — The  apparent  maintenance  requirement  per  day  per 
100  pounds  live  weight  of  ;Pig  A  (509  pounds)   was  0.139  pound  crude  protein, 
0.402  pound  carbohydrate,  0.032  pound  ether  extract;  of  Pig  B    (375  pounds), 
0.112   pound   crude  protein,   0.404   pound   carbohydrate,    0.032   pound    ether   ex- 
tract; of  Pig  C   (308  pounds),  O.M2  pound  protein,  0.401  pound  carbohydrate. 
0.032  pound  ether  extract.  Page  421 

7.  EXPERIMENT  No.  3.— The  apparent  maintenance  requirement  per  day  per 
100  pounds  live  weight  of  Pig  A   (415  pounds)   was  0.078  pound  protein,  0.228 
pound   carbohydrate,  and  0.029  pound  ether  extract;   of   Pig  B    (320  pounds), 
0.084  pound  protein,  0.213  pound  carbohydrate,  and  0.036  pound  ether  extract. 

Page  427 

8.  GENERAL  DISCUSSION.  Pages  431-435 

9.  CONCLUSIONS.  Page  435 

NOTE. — The  essential  points  of  this  bulletin  which  are  of  direct  interest 
to  the  general  swine  feeder  have  been  reported  and  discussed  in  Circulars  126. 
133,1  and  153  of  this  station.  The  present  publication  is  a  more  complete  and 
technical  report  of  certain  investigations  conducted  by  the  writer.  It  is  not 
designed  for  the  general  reader,  but  more  especially  for  students,  investigators, 
and  others  who  are  contemplating  or  engaged  in  similar  investigations. 

'Out  of  print. 


THE  MAINTENANCE  REQUIREMENT 
OF  SWINE 

BY  WIL/LJAM  DIETRICH,  ASSISTANT  CHIEF  IN  SWINE  HUSBANDRY 

INTRODUCTION 

A  certain  portion  of  the  food  eaten  by  an  animal  must  be  used 
for  maintenance ;  the  remainder  may  be  used  for  the  production  of 
food,  clothing,  or  energy  for  the  use  of  man.  If  it  is  possible, 
therefore,  to  determine  approximately  the  maintenance  require- 
ment, or  to  show  that  this  requirement  differs  under  different  con- 
ditions, one  of  the  necessary  fundamental  steps  will  have  been 
taken  in  solving  the  problem  of  swine  feeding. 

The  maintenance  requirement  may  be  defined  as  a  ration  con- 
taining enough  of  the  various  nutrients  (protein,  carbohydrate, 
ether  extract,  mineral  matter,  and  water)  to  support  the  animal 
when  doing  no  work  and  yielding  no  material  product;  in  other 
words,  the  minimum  food  supply  necessary  merely  to  maintain  the 
processes  essential  to  life  without  the  production  of  growth  or  of 
work.  In  this  bulletin  the  maintenance  ration  is  regarded  as  ap- 
proximately the  feed  required  to  maintain  the  live  weight  of  pigs 
without  either  gain  or  loss.  The  fact  is  recognized  that  the  mere 
maintenance  of  constant  live  weight  for  comparatively  short 
periods,  especially  by  young  animals,  is  not  necessarily  a  trust- 
worthy guide  in  the  determination  of  the  true  maintenance  re- 
quirement, notwithstanding  the  fact  that  up  to  the  present  time 
much  of  the  available  information  upon  this  subject  has  been  de- 
rived by  such  a  measure.  However,  the  length  of  time  of  the 
experiments  here  reported,  and  the  fact  that  in  some  of  them  the 
nitrogen  balance  was  determined,  adds  weight  to  the  significance  of 
the  results  obtained. 

•  EXPERIMENT  NO.  i 

The  first  data  obtained  by  the  writer  on  this  subject  were  gath- 
ered as  a  part  of  a  thesis  experiment1  conducted  at  the  Univer- 
sity of  Wisconsin  under  the  direction  of  Professor  W.  A.  Henry 
in  1898  and  1899.  These  results  are  given  in  the  following  dis- 
cussion. 


'A  review  of  this  experiment  is  given  in   the   i6th   Annual   Report  of  the 
Wisconsin  Agricultural  Experiment  Station  for  1899,  page  31. 

411 


412  BULLETIN   No.  163  \Junc, 

PLAN  OF  EXPERIMENT 

The  data  of  this  experiment  were  obtained  with  four  pigs  of 
mixed  breeding,  containing  Berkshire,  Poland-China,  and  Chester- 
White  blood.  They  were  the  same  age  and  nearly  the  same  weight 
and  were  treated  in  a  similar  manner.  Each  one  was  fed  by  itself, 
but  at  all  other  times  they  occupied  a  pen  in  common  in  the  hog 
house,  with  access  to  a  small  yard  on  the  outside. 

It  was  the  plan  of  this  experiment  to  start  with  pigs  weighing 
approximately  50  pounds.  The  amount  of  feed  required  for  main- 
tenance at  this  point  was  to  be  determined  as  accurately  as  possible. 
The  pigs  were  then  to  be  fed  up  to  100,  150,  and  200  pounds  live 
weight,  respectively,  with  maintenance  determinations  at  each  of 
these  stages  of  growth  and  fattening. 

Previous  to  the  time  of  the  beginning  of  this  experiment,  the 
pigs  had  been  fed  all  they  would  consume  readily.  It  was  thought 
that  by  gradually  reducing  their  feed  a  point  would  be  reached 
where  they  would  maintain  a  constant  live  weight,  the  ration  at 
such  point  representing  approximately  the  amount  of  feed  required 
for  maintenance;  and  that  with  a  further  reduction  in  the  ration 
the  pigs  would  lose  in  live  weight.  The  fact  is  recognized  that 
under  such  conditions  a  pig  might  be  losing  dry  matter  from  its 
body  and  at  the  same  time  replacing  it  with  water,  so  that  all  the 
facts  in  the  case  would  not  come  to  light.  Nevertheless,  an  experi- 
ment of  this  kind  shows  the  maintenance  requirements  so  far  as 
is  possible  without  the  use  of  a  respiration  calorimeter. 

The  feeds  used  in  the  maintenance  periods  of  this  experiment 
were  ground  corn,  wheat  middlings,  and  skim  milk.  The  meal 
used  during  the  first  eight  days  of  the  experiment  consisted  of 
ground  corn,  one  part,  and  wheat  middlings,  two  parts.  During 
the  remainder  of  the  experiment  it  consisted  of  equal  parts  of 
ground  corn  and  middlings.  The  meal  and  skim  milk  were  mixed 
according  to  the  existing  feeding  standards,  so  that  a  wider  nutri- 
tive ratio  was  obtained  in  each  successive  period  of  the  develop- 
ment of  the  pigs. 

Every  morning  before  they  received  their  feed,  the  pigs  were 
weighed.  Table  I  gives  the  quantities  fed  per  day  and  the  daily 
weights  of  the  pigs  during  the  four  periods  of  maintenance  feed- 
ing, except  that  in  each  case  the  first  day  of  a  period  is  the  last 
day  of  the  previous  full-feed  period. 

In  considering  the  data  for  the  5O-pound  pigs,  it  will  be  seen 
that  the  feed  record  starts  with  the  2d  day.  At  this  time  the  pigs 
received,  on  an  average,  2  pounds  of  meal  per  day,  which  was  a 
slight  reduction  from  the  full  feed  they  had  received  previously. 
During  the  first  28  days  of  the  experiment,  the  feed  was  slowly 


THE  MAINTENANCE  REQUIREMENT  OF  SWINE  413 

reduced,  but  the  average  live  weight  of  the  four  pigs  gradually 
increased  from  42.5  to  49.75  pounds  per  head.  During  the  5-day 
period  from  the  nth  to  the  I5th  day  the  pigs  gained  only  0.25 
pound;  consequently,  the  amount  of  feed  received  was  practically 
a  maintenance  ration  under  the  conditions  of  the  experiment  as 
they  existed  at  that  time. 

On  the  28th  day  the  feed  was  reduced  to  0.3  pound  meal  and 
1.2  pounds  skim  milk.  This  was  kept  constant  for  a  period  of 
7  days,  during  the  first  6  of  which  the  pigs  maintained  a  constant 
live  weight,  but  on  the  7th  they  lost  slightly;  and,  with  a  further 
reduction  in  the  feed  during  the  next  2  days,  they  lost  still  more. 
It  is  thus  seen  that  0.3  pound  meal  and  1.2  pounds  skim  milk  were 
required  for  the  maintenance  of  these  pigs  under  the  conditions  of 
this  experiment. 

Two  pounds  of  water  mixed  with  the  feeds  in  the  form  of  slop 
was  fed  each  pig  daily  from  the  I7th  to  the  36th  day  inclusive.  In 
addition,  the  pigs  were  offered  some  water  to  drink,  but  they  took 
very  little,  an  average  of  only  0.22  pound  per  head  per  day. 

A  similar  process  of  reduction  in  feed  was  repeated  during  the 
three  other  periods  of  the  experiment.  With  the  loo-pound  pigs 
the  maintenance  ration  was  found  to  be  that  fed  from  the  nth  to 
the  1 8th  day.  After  this  the  feed  was  reduced  to  see  whether  it 
would  cause  a  loss  in  live  weight.  On  the  2ist  day  there  was  a 
gain  made  on  the  reduced  quantity  of  feed,  but  at  this  time  the 
pigs  ate  some  of  the  bedding,  which  is  held  to  account  for  the  gain 
in  live  weight.  After  this  there  was  a  loss  in  live  w,eight  on  the 
reduced  quantity  of  feed. 

With  the  i5opound  pigs,  the  apparent  maintenance  ration  was 
reached  during  the  period  from  the  29th  to  the  35th  day,  and  con- 
sisted of  1.6  pounds  meal  and  1.6  pounds  skim  milk.  During  this 
time,  however,  the  pigs  lost  a  little  in  live  weight,  which  would 
seem  to  show  that  this  ration  was  at  least  a  small  enough  quantity. 
Because  there  was  a  slight  loss  in  live  weight  during  this  period, 
it  was  not  thought  necessary  to  make  further  reduction  in  feeds, 
but  the  pigs  were  fed  the  same  quantity  for  a  longer  time  for  the 
purpose  of  making  a  digestion  trial. 

With  the  2oo-pound  pigs,  the  apparent  maintenance  ration  was 
reached  during  the  period  from  the  22d  to  the  28th  day  inclusive, 
and  consisted  of  2  pounds  meal  per  day,  with  no  skim  milk.  This, 
apparently,  was  a  little  less  than  a  maintenance  ration,  as  the 
average  live  weight  of  the  pigs  was  reduced  from  201.5  to  200.75 
pounds  during  that  time. 

Table  2  shows  the  composition  of  the  feeds  used  in  these  tests, 
as  determined  by  the  writer  during  different  periods.  From  these 
data  the  amounts  of  digestible  nutrients  consumed  during  the  main- 
tenance periods  were  calculated. 


414 


BULLETIN  No.   163 


[June, 


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416 


BULLETIN  No.  163 


[June, 


TABLE  2. — PERCENTAGE  COMPOSITION  OF  FEEDS 


Feeds 

Crude 
protein 

Carbohydrates 

Ether 

extract 

Period  in 
which  used 

Nitrogen- 
free 
extract 

Crude 
fiber 

Ground   com    .  .        ... 

9.84 
9.73 

9.44 

71.72 
70.91 
72.01 

2.42 
2.39 

2.01 

3.91 
3.87 
3.65 

1  and  2 
3 

4 

Ground  corn    

Ground  corn    

Wheat   middlings    .... 
Wheat  middlings    .... 
Wheat  middlings    .... 

16'.  67 
16.62 
17.13 

56.79 
56.61 
52.99 

6.76 
6.73 

6.77 

4.74 
4.73 
5.54 

1  and  2 
3 

4 

Skim   milk    

3.23 
3.41 
2.81 

4.80 
5.04 
4.43 

.09 
.12 
.08 

1 
2 
3 

Skim   milk         

Skim   milk    

The  coefficients  of  digestibility  were  also  determined  during 
the  maintenance  and  full-feed  periods  with  two  of  the  I5o-pound 
pigs.  The  averages  of  these  factors  for  the  two  pigs  used  during 
the  maintenance  period  are  as  follows :  crude  protein,  78 ;  nitro- 
gen-free extract,  85 ;  ether  extract,  76.  During  the  full-feed 
period  the  f ollotf  m*g  factors  were  obtained :  crude  protein,  76 ; 
nitrogen-free  extract,  86;  crude  fiber,  22;  ether  extract,  66.  The 
averages  of  these  are  as  follows :  crude  protein,  77 ;  nitrogen-free 
extract,  85.5;  crude  fiber,  22;  ether  extract,  71.  Calculating  by 
the  use  of  these  factors  the  amounts  of  digestible  nutrients  fed  dur- 
ing the  different  periods,  the  data  given  in  Table  3  were  obtained. 

From  Table  3  it  will  be  noticed  that  the  quantities  of  feed  re- 
quired for  maintenance  by  the  5O-pound  pigs  were  0.3  pound  meal 
(one-half  consisting  of  ground  corn  and  one-half  of  middlings)  and 
1.2  pounds  skim  milk;  by  the  loo-pound  pigs,  0.8  pound  meal  and 
1.6  pounds  skim  milk;  by  the  I5o-pound  pigs,  1.6  pounds  meal 
and  1.6  pounds  skim  milk;  while  the  2OO-pound  pigs  were  nearly 
maintained  on  2  pounds  meal  with  no  milk,  but,  as  pointed  out 
above,  this  probably  was  too  small  a  quantity. 

The  table  shows  that  the  5O-ponnd  pigs  were  maintained  on 
0.75  pound  of  feed  per  100  pounds  live  weight,  as  a  daily  ration, 
the  loo-pound  pigs  on  0.86  pound,  the  i5O-pound  pigs  on  I  pound, 
and  the  2OO-pound  pigs  were  nearly  maintained  on  0.88  pound.  By 
referring  to  the  next  column  it  will  be  seen  that  the  amount  of 
digestible  crude  protein  in  the  maintenance  ration  for  the  5O-pound 
pigs  was  o.i 21  pound  per  day;  for  the  loo-pound  pigs,  0.124 
pound;  for  the  I5o-ponnd  pigs,  0.131  pound;  and  for  the  200- 
pound  pigs,  o.i 02  pound. 

The  next  column  gives  the  digestible  carbohydrates  daily  per 
100  pounds  live  weight.  The  results  seem  to  show  that  the  50- 
pound  pigs  required  0.434  pound  per  day;  the  loo-pound  pigs, 
0.517  pound;  the  i5O-pound  pigs,  0.633  pound;  and  the  2OO-pound 
pigs,  0.549  pound. 


1913} 


THE  MAINTENANCE  REQUIREMENT  OF  SWINE 


TABLE  3. — MAINTENANCE  RATION   FOR   SWINE  AS   DETERMINED  IN   EXPERIMENT 

No.  1 
(Expressed  in  pounds  per  day) 


Weight 
of 
pigs 

Feeds  per  head 

Total 
feed 
per  100 
pounds 
live 
weight 

Digestible  nutrients  and  metabolizable 
energy  per  100  pounds  live  weight 

Nutri- 
tive 

ratios 

Meal 

Skim 
milk 

Crude 
protein 
(Nx6.25) 

Carbohydrates 

Ether 
extract 

Metabo- 
lizable 
energy,1 
therms 

Nitrogen- 
free  ex- 
tract 

Crude 
fiber 

50 
100 
150 
200 

.3 
.8 
1.6 
2.0 

1.2 
1.6 
1.6 
0. 

.75 
.86 
1.00 

.88 

.121 
.124 
.131 
.102 

.428 
.509 
.622 
.539 

.006 
.008 
.011 
.010 

.020 
.026 
.033 
.033 

.897 
1.317 
1.806 
1.718 

1:3.9 
1:4.3 
1:5.3 
1:5.3 

'The  metabolizable  energy  of  a  ration  is  the  energy  which  can  be  liberated 
and  utilized  in  the  animal  body ;  or.  the  gross  energy  less  that  contained  in  the 
feces,  urine,  and  intestinal  gases.  The  metabolizable  energy  of  the  rations  has 
been  calculated  from  the  amount  of  digestible  nutrients,  using  the  following 
factors  :  Calories  per  pound 

Digestible   protein    1860 

Digestible  •  nitrogen-free  extract   1905 

Digestible  crude  fiber    1588 

Digestible  ether   extract    399.? 

One  therm  equals  1000  calories.  It  is  generally  accepted  that  the  metabolism 
of  the  animal  body  is  proportional  to  the  surface  of  the  animal,  and  further, 
that  the  surfaces  of  two  animals  of  the  same  species  are  proportional  to  the 
two-thirds  powers  of  their  weights.  Therefore,  the  metabolizable  energy  given 
above  has  been  calculated  on  the  basis  of  the  two-thirds  powers  of  the  body 
weights. 

By  referring  to  the  first  part  of  the  table  it  will  be  seen  that 
the  loo-pound  pigs  received,  proportionately,  a  smaller  quantity  of 
skim  milk  than  did  the  5O-pound  pigs,  while  the  i5O-pound  pigs 
received  a  still  smaller  quantity,  and  the  2OO-pound  pigs  received 
none  at  all.  Since  skim  milk  is  a  nitrogenous  feed,  it  will  be  ob- 
served that  by  this  method  of  feeding  the  relative  quantity  of  crude 
protein  in  the  daily  ration  was  gradually  reduced  as  the  pigs  grew 
older.  As  the  last  column  of  the  table  shows,  the  nutritive  ratios 
of  the  rations  were  materially  widened  from  the  first  to  the  third 
periods. 

EXPERIMENT  NO.  2 

For  further  evidence  as  to  the  amount  of  feed  and  of  digestible 
nutrients  required  for  maintenance,  the  results  of  another  experi- 
ment that  was  made  during  the  winter  of  1905-06  at  this  station 
are  here  given. 

Three  pigs,  a  Berkshire  3  years  old,  a  Poland-China  \l/2  years 
old,  and  a  Poland-China  i  year  old  (designated  A,  B,  and  C,  re- 
spectively) were  fed  in  separate  box  stalls  where  their  feces  and 
urine  could  be  collected.  The  pigs  were  kept  confined  in  these 
stalls  except  when  they  were  taken  out  to  be  weighed  and  exercised 
in  the  morning  and  driven  several  hundred  feet  for  exercise  in  the 
afternoon. 


418  BULLETIN  No.  163  [June, 

After  the  three  pigs  had  been  on  full  feed  for  nine  days,  their 
daily  allowance  was  gradually  reduced  during  a  period  of  two 
weeks,  so  that  at  the  end  of  this  period  they  were  receiving  amounts 
of  digestible  nutrients  that  were  considered  sufficient  for  mainte- 
nance but  not  enough  to  produce  material  gains  in  live  weight. 

The  feeds  used  during  the  full- feed  period  were  ground  corn, 
wheat  bran,  and  wheat  middlings.  During  the  reduction  period 
the  ground  corn  and  middlings  were  gradually  reduced  and  the 
bran  increased  until  the  ration  was  one  of  bran  alone.  It  was 
found,  however,  that  all  the  pigs  would  not  eat  enough  of  an  all-bran 
ration  for  maintenance;  consequently,  after  the  first  few  days  of 
this  kind  of  feeding,  part  of  the  bran  was  replaced  with  ground 
corn  and  tankage.  The  change  was  made,  however,  so  that  the 
total  amounts  of  digestible  nutrients  remained  practically  the  same. 

EXPERIMENTAL,  DATA 

Table  4  gives  a  complete  record  of  the  feeds  used  and  of  the 
live  weights  of  the  three  pigs  from  the  time  full  feed  was  discon- 
tinued until  a  week  after  the  final  maintenance  period. 

As  is  shown  by  the  table,  the  pigs  maintained  practically  con- 
stant weight  from  the  i9th  to  the  29th  day,  such  fact  indicating  that 
the  amounts  and  proportions  of  feeds  received  at  this  time  appar- 
ently were  sufficient  for  maintenance.  At  the  dose  of  this  period, 
the  ration  was  reduced  still  further  to  see  if  this  reduced  quantity 
would  result  in  a  loss  of  live  weight.  During  the  first  four  days 
following  this  reduction,  Pig  A  lost  2  pounds,  and  Pigs  B  and  C 
each  lost  3  pounds  in  live  weight.  On  continuing  this  latter  ration 
for  a  longer  time,  however,  it  was  found  that  the  pigs  maintained 
their  slightly  lower  live  weights  on  this  reduced  quantity  of  feed 
without  the  slightest  fluctuation  until  the  44th  day.  At  this  time 
they  were  given  still  another  reduction  in  feed,  but  they  lost  in  live 
weight  from  I  to  3  pounds  per  day  during  the  entire  following 
week.  This  reduction  of  feed,  however,  was  of  considerable  mag- 
nitude. It  is  not  known  whether,  if  this  quantity  of  feed  had  been 
continued  for  a  longer  time,  it  would  also  have  maintained  the  live 
weights  of  these  hogs. 

During  the  period  from  the  I9th  to  29th  day  inclusive,  the  pigs 
were  receiving  in  their  daily  rations  the  following  amounts  of  di- 
gestible nutrients  in  pounds  per  100  pounds  live  weight: 


Pig 

Digestible 
crude 
protein 

Digestible 
carbohy- 
drate 

Digestible 
ether 
extract 

A 
B 
C 

.15 

.15 

.15 

.44 

.49 
.40, 

.058 
.034 
.035 

THE  MAINTENANCE  REQUIREMENT  OF  SWINE 


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THE  MAINTENANCE  REQUIREMENT  OF  SWINE 


421 


These  quantities  were  obtained  by  using  78,  88,  and  80,  re- 
spectively, as  the  coefficients  of  digestibility  for  crude  protein,  car- 
bohydrates, and  ether  extract,  the  following  being  the  percentage 
composition  of  the  feeds  used : 


Crude  protein 

Carbohydrates 

Ether  extract 

Corn    •  

10  26 

74  66 

3.75 

Wheat   bran    

14  62 

61  93 

4.25 

Tankage   

67.95 

8.75 

On  the  3Oth  day,  after  the  amount  of  feed  had  been  reduced  to 
determine  whether  or  not  they  would  lose  in  weight,  the  pigs  were 
receiving  the  amounts  of  digestible  nutrients  per  day  per  100 
pounds  live  weight  shown  in  Table  5. 

TABLE  5. — MAINTENANCE   RATION   FOR   SWINE  AS   DETERMINED  IN   EXPERIMENT 

No    2 

(Expressed  in  pounds  per  day) 


Weight 
of 
pigs 

Feeds  per  head 

Total 
feed 
per  100 
pounds 
live 
weight 

Digestible  nutrients  per  100 
pounds  live  weight 

Ground 
corn 

Wheat 
bran 

Tank- 
age 

Crude 
protein 

Carbo- 
hydrate 

Ether 
extract 

Metab- 
olizable 
energy, 
therms 

A-509 
B-375 
C-308 

1.0 
.4 
.4 

4.0 
3.6 

2.8 

.4 
.2 
.2 

1.06 
1.12 

1.10 

.139 
.112 
.112 

.402 
.404 
.401 

.032 
.032 
.032 

1.981 
1.717 
1.600 

Since  on  these  last  amounts  of  digestible  nutrients  the  pigs 
maintained  constant  weight,  altho  at  a  slight  reduction  from  that 
of  the  previous  two  weeks  of  maintenance  feeding,  a  still  further 
reduction  in  feed  was  made  on  the  44th  day,  as  mentioned  above, 
to  approximately  0.08  pound  crude  protein,  0.25  pound  carbo- 
hydrate, and  0.02  pound  ether  extract,  with  the  result  that  they  lost 
very  materially  in  live  weight. 

The  data  in  Table  5  show  that  the  feed  required  for  mainte- 
nance was  about  1.09  pounds  per  day  per  100  pounds  live  weight. 
This  is  a  much  larger  quantity  than  is  cited  in  Experiment  No.  I 
(0.87  pound),  but  it  must  be  remembered  that  the  ration  in  the 
second  experiment  was  made  up  largely  of  wheat  bran. 

Under  the  heading  "Digestible  nutrients  per  100  pounds  live 
weight,"  it  will  be  noticed  that  Pig  A  required  0.139  pound  crude 
protein  for  maintenance  while  B  and  C  were  maintained  on  0.112 
pound.  This  difference  is  due  to  the  fact  that  when  the  reduction 
in  the  feed  was  made  on  the  3Oth  day,  the  ration  for  Pig  A,  thru 
some  error  in  calculation,  was  not  reduced  as  much  as  that  of  the 
others. 


422  BULLETIN  No.  163  [June, 

Whether  or  not  the  pigs  would  have  been  maintained  on  a 
slightly  smaller  quantity  is  not  known,  but  from  the  foregoing  re- 
sults it  would  seem  that  the  0.08  pound  protein,  0.25  pound  carbo- 
hydrate, and  0.02  pound  ether  extract,  to  which  the  ration  was 
reduced  on  the  44th  day,  was  not  sufficient,  at  least  under  the 
prevailing  conditions  of  the  experiment.  This  reduction,  how- 
ever, was  of  considerable  magnitude. 

In  this  second  experiment  the  pigs  were  apparently  maintained 
on  a  smaller  quantity  of  nutrients  than  in  the  first  one.  There  are 
a  number  of  possible  reasons  for  this  fact.  First,  instead  of  dis- 
continuing the  experiment  as  soon  as  the  pigs  showed  a  loss  in 
weight  after  the  reduction  in  the  food  intake  following  the  first 
maintenance  trial,  as  was  done  in  the  first  experiment,  they  were 
continued  on  the  reduced  quantities  of  feed  for  a  longer  time. 
Instead  of  continuing  to  lose  in  weight,  the  pigs,  contrary  to  expec- 
tations, maintained  constant  weight  for  a  period  of  ten  days,  which 
•would  apparently  indicate  that  this  smaller  quantity  of  feed  at  this 
time  was  sufficient  for  maintenance.  In  other  words,  it  is  possible 
that  if  the  first  experiment  had  been  continued  longer  after  the  re- 
duction in  the  food  intake  had  been  made,  the  pigs  later  might  have 
been  able  to  maintain  constant  body  weight.  Second,  relatively  more 
protein  was  supplied  in  the  ration  of  this  second  experiment  than 
in  that  of  the  first  experiment.  This  factor  may  have  had  an  in- 
fluence in  making  the  ration  more  efficient  for  maintenance.  Third, 
the  pigs  used  in  this  experiment  were  not  of  the  same  breed,  nor  of 
the  same  age,  weight,  or  condition  as  those  used  in  the  first  experi- 
ment. 

EXPERIMENT  NO.  3 

Two  Berkshire  barrows  were  used  that  were  farrowed  in  Sep- 
tember, 1906.  During  the  summer  of  1907,  they  were  allowed  to 
run  on  pasture  with  very  scanty  grain  rations.  It  was  thought  that 
this  treatment  would  get  them  into  the  best  possible  condition  for 
this  experiment.  On  November  12,  1907,  they  were  put  into  their 
crates  for  the  preliminary  feeding.  These  crates  were  just  long 
enough  for  the  pigs  to  stand  up  or  lie  down  conveniently,  and  were 
arranged  so  that  the  feces  could  be  collected  at  the  back  end  of  the 
crate  where  they  were  dropped.  The  urine  was  collected  by  means 
of  a  zinc  bottom  inclining  toward  the  middle  and  leading  into  a 
pan,  placed  underneath,  which  was  enclosed  so  as  to  prevent  evapo- 
ration. The  front  end  of  this  sheet  of  metal  sloped  forward  in 
order  to  carry  away  any  saliva  that  might  be  dropped  from  the 
mouth  of  the  pig.  It  was  noticed  that  this  occurred  at  times. 

It  is  thought  necessary  in  an  experiment  of  this  kind  to  keep 
pigs  in  their  respective  places  for  a  considerable  length  of  time  in 


THE  MAINTENANCE  REQUIREMENT  OF  SWINE  423 

order  to  accustom  them  to  this  manner  of  living,  to  adjust  the 
crates  properly,  and  to  determine  just  the  amount  of  feed  that  will 
be  consumed  readily.  The  experiment  proper  started  on  De- 
cember 9,  making  a  preliminary  feeding  period  of  nearly  a  month, 
and  closed  June  3,  1908.  At  the  beginning  of  the  experiment,  the 
two  pigs  weighed  320  and  240  pounds  respectively,  and  at  the  close, 
470  and  350  pounds.  The  pigs  were  taken  out  of  their  crates  twice 
a  day  for  exercise. 

After  the  pigs  had  been  on  feed  from  December  9,  1907,  to 
February  21,  1908,  inclusive,  the  maintenance  periods  started.  The 
data  of  this  part  of  the  experiment  are  shown  in  Table  6.  The 
feed  was  gradually  reduced  (for  Pig  A  during  two  weeks'  time, 
and  for  B,  during  four  weeks'  time)  to  approximately  the  main- 
tenance quantity  determined  in  the  previous  experiments,  and  this 
was  fed  to  A  for  a  period  of  four  weeks  and  to  B  for  a  period  of 
two  weeks.  Following  this  was  a  fasting  period  of  eight  days 
(47th  to  54th  day  inclusive). 

Following  the  fasting  period  there  were  ten  consecutive  5-day 
periods,  two  of  which  are  included  in  Table  6.  During  the  first  ten 
days  following  fasting,  the  pigs  were  fed  a  supposed  maintenance 
quantity  of  feed,  which  was  somewhat  less  than  that  fed  previous 
to  the  fasting  period.  The  entire  quantity  of  water  fed  to  these 
pigs  was  given  to  them  in  their  slop  and  was  more  or  less  constant. 
On  several  occasions  they  were  offered  water  to  drink,  but  refused 
to  take  any. 

All  feeds  used  were  analyzed,  and  both  feces  and  urine  were 
subjected  to  a  complete  chemical  analysis  to  determine  as  nearly  as 
possible  the  total  amount  and  the  nature  of  the  metabolism  that 
takes  place  in  a  pig  under  these  various  conditions. 

EXPERIMENTAL  DATA 

The  following  table  gives  a  complete  record  of  the  feeds  and 
water  consumed  by  the  pigs  daily,  and  also  their  daily  live  weights 
for  the  part  of  the  experiment  that  pertains  to  the  subject  in  hand. 

It  will  be  seen  from  this  table  that  both  pigs  made  some  gain  in 
live  weight  during  the  first  twelve  days  of  this  part  of  the  experi- 
ment, and  that  Pig  B  continued  to  make  gains  up  to  the  24th 
day,  while  A  rema  ned  practically  constant.  This  difference  was 
due  to  the  fact,  as  stated  above,  that  the  ration  for  Pig  A  was 
reduced  more  -rapidly  than  that  for  Pig  B.  At  about  the  28th  day 
(Period  10)  the  rations  for  both  pigs  had  been  reduced  to  a  quantity 
that  was  supposed  to  be  a  maintenance  ration,  and  the  live  weights 


424 


BULLETIN  No.  163 


[June, 


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426 


BULLETIN  No.  163 


[June, 


were  apparently  maintained.  Following  Period  10,  the  ration  were 
still  further  reduced  to  make  sure  that  they  would  be  low  enough. 
The  pigs  maintained  fairly  constant  live,  weight  on  the  reduced 
quantity  of  nutrients  until  about  the  42d  day,  after  which  there 
was  a  tendency  for  them  to  lose  in  live  weight.  This  would  seem 
to  indicate  that  the  amounts  of  feed  given  at  this  time  supplied  a 
quantity  of  nutrients  that  might  be  a  little  below  the  maintenance 
requirement. 

During  the  fasting  period  the  pigs  lost  steadily  in  live  weight. 
Following  this  period  they  were  given  less  food  for  a  period  of  ten 
days  than  they  had  received  just  previous  to  it.  Nevertheless,  they 
maintained  fairly  constant  live  weight. 

All  this  seems  to  indicate  very  strongly  that  the  maintenance 
requirement  of  swine  is  not  constant  but  varies  under  different  con- 
ditions. When  the  ration  is  reduced,  the  maintenance  requirement 
also  seems  to  become  lowered. 

TABLE  7. — PERCENTAGE  COMPOSITION  OF  FEEDS 
(Grindley  and  Emmett,  Analysts) 


Feed 

Water 

Crude 
protein 

Carbo- 
hydrate 

Ether 
extract 

Ash 

Nitro- 
gen 

Phos- 
phorus 

Before  Fasting 


Ground  corn  
Red  dog  flour  
Tankage  

13.40 
11.59 
7  09 

8.69 
17  .'87 
58  90 

73.98 
73.81 
10  13 

2.76 
1.55 
14  23 

1.38 
3.54 
9.63 

1.391 
1.498 
9.424 

.26 
.81 
127 

Pork  cracklings  .  .  . 

4.89 

54.17 

2.00 

35.67 

2.00 

8.669 

.27 

After  Fasting 


Ground  corn    

14.16 

8.33 

73.29 

2\88 

1.32 

1.333 

.253 

Red   dog  flour  
Tankage   

11.82 
9.19 

17.86 
57.57 

73.74 
9.91 

1.55 
13.91 

3.54 
9.42 

1.497 
9  211 

.800 
1  240 

Pork  cracklings   .  .  . 

5.41 

53.88 

1.99 

36.72 

2.00 

8.622 

.265 

Table  7  gives  the  percentage  composition  of  the  various  feeds 
that  were  used  during  the  maintenance  portion  of  the  experiment. 
In  general,  it  should  be  noted  that  red  dog  flour  contains  about 
twice  as  much  crude  protein  as  does  ground  corn,  and  that  it  con- 
tains considerably  less  ether  extract  and  a  great  deal  more  ash  and 
phosphorus.  Tankage  contains  less  water  than  either  ground  corn 
or  red  dog  flour.  It  contains  a  very  high  percentage  of  crude 
protein  besides  considerable  ether  extract,  and  is  high  in  ash  and 
phosphorus  also.  Pork  cracklings  are  comparable  to  tankage  in 
crude  protein,  but  they  contain  very  much  more  ether  extract  and 
less  ash  and  phosphorus.  The  phosphorus  content  of  cracklings  is 
practically  the  same  as  that  of  ground  corn. 


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428  BULLETIN  No.  163  [June, 

The  coefficients  of  digestibility  used  in  calculating  the  amounts 
of  digestible  nutrients  consumed  were  determined  during  the  pro- 
gress of  the  experiment.  They  are  approximately  as  follows: 
crude  protein,  80;  carbohydrate,  90;  ether  extract,  90.  On  this 
basis  the  two  pigs  were  receiving,  during  the  maintenance  periods, 
the  amounts  of  feeds  and  digestible  nutrients  recorded  in  Table  8. 

As  will  be  seen  from  Table  8,  these  pigs  received  very  small 
quantities  of  total  feed  during  the  maintenance  periods.  During 
Period  10,  when  they  maintained  constant  live  weight,  they  received 
0.65  and  0.67  percent  of  feed  respectively,  based  on  their  live 
weights.  During  Period  n,  when  they  maintained  their  live 
weights  equally  well,  these  quantities  had  been  reduced  to  0.46 
and  0.51  percent  respectively.  These  quantities  were  still  further 
reduced  during  Period  12,  but  the  pigs  did  not  maintain  their  live 
weights.  After  fasting,  the  two  pigs  received  only  0.43  and  0.44 
percent  of  feed  respectively,  and  maintained  their  live  weights 
after  gaining  a  little  immediately  following  the  period  of  fasting. 

During  Period  10,  when  the  pigs  were  maintaining  their  live 
weights,  they  were  receiving  an  average  of  p.i  pound  of  digestible 
crude  protein,  0.376  pound  of  digestible  carbohydrates,  and  0.038 
pound  of  digestible  ether  extract.  During  Period  1 1  these  quanti- 
ties had  been  reduced  to :  crude  protein,  0.084 ;  carbohydrate,  0.258 ; 
and  ether  extract,  0.032 ;  and  still  the  pigs  were  maintaining  their 
live  weights.  During  Period  12  the  pigs  lost  a  little  in  live  weight; 
consequently  the  nutrients  they  received  at  that  time  are  not  con- 
sidered sufficient  for  maintenance  under  the  conditions  of  the 
experiment  then  existing.  After  the  period  of  fasting,  they  re- 
ceived the  following  amounts  of  digestible  nutrients :  protein,  0.079 ; 
carbohydrate,  0.221 ;  and  ether  extract,  0.033.  These  quantities 
are  considerably  lower  than  those  of  any  previous  period  of  this 
experiment  and  decidedly  lower  than  those  of  either  of  the  two  pre- 
vious experiments ;  but  still  the  pigs  maintained  their  live  weights. 

Table  10  gives  the  percentage  composition  of  the  fresh  feces 
and  urine.  The  data  show  that  the  feces  of  Pig  A  contained  more 
water  than  those  of  Pig  B,  but  that  the  feces  of  Pig  B  contained  a 
higher  percentage  of  crude  protein  and  of  carbohydrates  than  did 
those  of  Pig  A. 

Table  n,  giving  the  percentage  chemical  composition  of  the 
water- free  feces,  shows  that  before  fasting,  the  feces  of  Pig  A 
contained  less  crude  protein  and  more  ash  than  those  of  Pig  B, 
and  that  in  ether  extract  and  carbohydrate  the  feces  of  the  two 
pigs  were  quite.comparable  but  that  the  quantities  appearing  in  the 


THE  MAINTENANCE  REQUIREMENT  OF  SWINE 


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BULLETIN  No.  163 


[June, 


different  periods  were  somewhat  variable.  It  also  shows  that  after 
fasting,  as  well  as  before,  the  feces  of  Pig  A  contained  less  crude 
protein  and  more  ash  than  those  of  Pig  B.  In  carbohydrate  con- 
tent the  feces  of  the  two  pigs  were  practically  the  same. 

TABLE  11. — PERCENTAGE  COMPOSITION  OF  THE  WATER-FREE  FECES 
(Grindley  and  Emmett,  Analysts) 


Days 

Period 

Pig 

Crude 
protein 

Ether 
extract 

Carbo- 
hydrate 

Ash 

Before  Fasting 


27-29 

10 

A 

28.63 

5.34 

50.98 

15.05 

" 

JO 

B 

31.38 

6.15 

58.69 

13.78 

34-36 

11 

A 

30.11 

6.66 

47.11 

16.12 

« 

11 

B 

31.13 

5.23 

47.72 

15.92 

43-46 

12 

A 

30.95 

5.37 

46.03 

17.65 

" 

12 

B 

35.53 

4.15 

44.52 

15.80 

After  Fasting 


55-59 

14 

A 

25.62 

6.31 

44.92 

23.15 

57-59 

14 

B 

31.76 

5.87 

44.37 

18.00 

60-64 

15 

A 

28.52 

4.25 

46.42 

20.81 

* 

15 

B 

34.66 

3.23 

47.91 

14.20 

Table  12  gives  the  nitrogen  balance,  and  the  water  balance  as 
far  as  it  could  be  determined  from  the  feces  and  urine  alone  with- 
out the  use  of  a  respiration  calorimeter. 

TABLE  12. — BALANCES  FOR  WATER,  NITROGEN,  PROTEIN,  AND  BODY  TISSUE 
(Expressed  in  pounds  per  day  per  100  pounds  live  weight) 


Days 

Period 

Pig 

Water 

Nitrogen 

Protein 
(Nx6.25) 

Body 
tissue 
(orotein  x  4) 

Name 

Weight 

Before  Fasting 


27-29 

10 

A 

431 

.2471 

.0007 

.0044 

.0175 

10 

B 

336 

.9292 

.0007 

.0044 

.0175 

34-36 

11 

A 

431 

.2726 

.0028 

.0155 

.0620 

" 

11 

B 

336 

.5916 

.0017 

.0108 

.0432 

43-46 

12 

A 

427 

.1195 

.0020 

.0134 

.0536 

" 

12 

B 

332 

.2830 

.  0023 

.0144 

.0576 

After   Fasting 


55-59 

14 

A 

415.3 

.5349 

.0040 

.0249 

.0996 

57-59 

14 

B 

319.8 

.8640 

.0041 

.0256 

.1024 

60-64 

15 

A 

415.7 

.3209 

.00004 

.0003 

.0012 

" 

15 

B 

319.5 

.6956 

.0013 

.0081 

.0324 

The  data  of  Table  12  show  that  both  pigs  maintained  plus  ni- 
trogen balances  during  Periods  10,  14,  and  15,  with  the  exception 
that  Pig  A  had  a  very  small  minus  balance  during  Period  15,  so 
small,  however,  that  it  is  practically  negligible.  This  shows  that 
the  pigs  at  these  times  had  sufficient  protein  in  their  ration  for 


THE  MAINTENANCE  REQUIREMENT  OF  SWINE  431 

maintenance.  During  Periods  n  and  12  there  was  not  enough 
protein  in  the  ration  to  maintain  nitrogen  equilibrium  under  the 
existing  conditions.  Since  the  pigs  received  practically  the  same 
quantity  of  protein  during  Periods  14  and  15  (after  fasting)  as 
they  did  during  Periods  n  and  12  (before  fasting),  it  is  evident 
that  the  fasting  period  exerted  an  influence  upon  the  maintenance 
requirement.  It  seemingly  had  the  effect  of  making  the  pig  a 
somewhat  more  economical  machine. 

GENERAL  DISCUSSION 

One  of  the  most  obvious  facts  brought  out  by  the  data  pre- 
sented in  this  bulletin  is  the  apparent  variability  in  the  maintenance 
requirement  of  swine. 

In  the  first  experiment,  the  5<>pound  pigs  were  practically 
maintained  in  live  weight  from  the  nth  to  the  I5th  day  of  the  ex- 
periment, inclusive.  From  the  24th  to  the  2/th  day  inclusive,  when 
they  were  fed  only  about  60  percent  of  the  quantity  of  feed  given 
them  during  the  period  mentioned  above,  they  fully  maintained 
their  live  weights;  in  fact,  they  gained  on  an  average  y?.  pound 
during  the  4-day  period,  while  during  the  former  5-day  period  they 
gained  on  an  average  only  Y^  pound.  With  a  still  further  reduction 
in  feed  to  somewhat  less  than  half  the  quantity  which  they  received 
from  the  nth  to  the  I5th  day  inclusive,  they  again  maintained  their 
live  weights.  However,  it  should  be  noted  in  this  connection  that 
these  same  pigs,  when  they  weighed  100,  150,  and  200  pounds,  did 
not  exhibit  this  apparent  variability  in  maintenance  requirements. 
It  is  possible  that  this  difference  in  behavior  was  due  to  the  fact 
that  in  the  latter  case  the  rations  were  reduced  more  rapidly ;  also 
that  each  of  the  latter  periods  was  preceded  by  a  maintenance 
period  lasting  for  a  few  weeks. 

In  the  second  experiment,  the  pigs  maintained  their  live  weights 
very  constant  from  the  I9th  to  the  29th  day  inclusive.  With  a 
reduction  in  the  feed  amounting  to  about  n  percent  on  the  3Oth 
day,  they  again  maintained  their  live  weights  on  the  reduced 
quantity  of  feed  beginning  with  the  33rd  day. 

In  the  third  experiment,  the  pigs  maintained  their  live  weights 
during  several  different  periods  from  the  27th  to  the  64th  day  of 
the  experiment,  on  distinctly  different  quantities  of  feeds. 

The  author  as  yet  has  found  no  reference  to  other  maintenance 
experiments  upon  pigs  in  which,  after  the  apparent  maintenance 
ration  was  found,  the  effects  of  a  further  reduction  in  the 
ration  upon  the  live  weight  were  determined.  The  experi- 
mental data  here  given  clearly  show  that  the  live  weight  of  one  and 
the  same  pig  may  be  maintained  at  different  times  and  under  dif- 
ferent conditions  upon  distinctly  different  quantities  of  food  nutri- 


432  BULLETIN  No.  163  [June, 

ents.  The  results  indicate  that  the  pigs,  after  being  kept  for  some 
time  upon  a  maintenance  ration,  get  into  such  condition  that  they 
can  utilize  the  food  constituents  to  better  advantage  for  purposes 
of  maintenance  than  they  can  when  given  larger  quantities  of  the 
same  feed  preceding  the  maintenance  period. 

This  finding  with  regard  to  swine  is  in  agreement  with  the  re- 
sults obtained  by  Waters1  in  experiments  with  steers,  from  which 
he  draws  the  following  conclusions:  "Apparently  the  animal  or- 
ganism (steers),  when  kept  for  a  long  period  of  time  on  a  low  nu- 
tritive plane,  as  in  the  case  of  maintenance  animals,  gets  on  a  more 
economical  basis  than  when  more  liberally  fed.  For  example,  if 
we  reduce  the  feed  of  an  animal  that  has  been  previously  liberally 
nourished,  to  a  point  where  for  a  month  or  more  there  is  a  small 
loss  in  weight,  an  equilibrium  will  later  be  established  and  subse- 
quently the  animal  may  increase  in  weight,  the  quantity  and  qual- 
ity of  the  food  remaining  the  same.  Thus,  a  ration  that  was  in- 
sufficient to  sustain  live  weight  at  first  may  be  capable  later  of 
maintaining  the  animal  at  a  stationery  body  weight,  and  still  later 
of  causing  an  increase  in  weight.  Digestion  experiments  with  a 
number  of  animals  indicate  that  a  part  of  this  is  due  to  the  more 
complete  digestion  of  the  food  by  the  animal  on  a  low  nutritive 
plane,  but  so  far  as  the  experiments  have  thus  far  progressed  there 
does  not  seem  to  have  been  a  sufficient  increase  in  the  degree  to 
which  the  food  has  been  digested  to  account  for  all  the  increased 
efficiency  in  the  ration  noted." 

The  results  obtained  with  the  pigs  are  also  in  accord  with  those 
obtained  by  Mumford,  Grindley,  Hall,  and  Emmett  in  an  extended 
investigation2  by  this  department  in  which  it  has  been  clearly  dem- 
onstrated that  sjeers  kept  upon  a  maintenance  ration  utilize  their 
feed  more  completely  than  do  full-fed  steers;  and  further,  that 
steers  kept  continually  upon  maintenance  for  a  long  period  of  time 
become  more  and  more  economical,  or  in  other  words,  they  gradu- 
ally get  into  such  a  condition  that  they  can  maintain  themselves 
upon  smaller  and  smaller  quantities  of  the  same  feed. 

On  the  other  hand,  it  is  not  apparent  from  the  digestion  experi- 
ments that  were  made  in  connection  with  these  maintenance  ex- 
periments that  these  pigs,  when  upon  a  maintenance  ration,  digested 
significantly  greater  quantities  of  the  food  nutrients  than  they  did 
"when  given  a  full-feed  allowance.  A  further  discussion  of  the 
probable  explanation  for  this  apparent  variability  in  the  utilization 
of  food  by  pigs  will  be  considered  in  a  subsequent  bulletin. 

'Proc.  Soc.  Prom.  Agr.  Sci.,  390S. 

"Unpublished  manuscript  of  the  Department  of  Animal  Husbandry,  Uni- 
versity of  Illinois. 


THE  MAINTENANCE  REQUIREMENT  OF  SWINE  433 

As  seen  from  the  data  of  the  first  experiment  given  in  Table  3, 
page  4 1 7,  pigs  of  the  same  mixed  breeding,  ranging  in  weight  from 
50  to  150  pounds  live  weight,  were  maintained  on  0.12  to  0.13 
pound  of  digestible  crude  protein,  0.43  to  0.62  pound  of  digestible 
nitrogen-free  extract,  0.006  to  o.on  pound  of  crude  fiber,  and 
0.020  to  0.033  pounds  of  ether  extract,  daily,  per  100  pounds  live 
weight.  The  2oo-pound  pigs  were  not  quite  maintained  on  o.  10 
pound  of  crude  protein,  0.54  pound  of  nitrogen-free  extract,  o.oi 
pound  of  crude  fiber,  and  0.033  pound  of  ether  extract.  The  me- 
tabolizable  energy  required  for  maintenance  by  the  50-,  100-,  150-, 
and  2oo-pound  pigs  were  0.897,  I-3I7?  1-806,  and  1.718  therms 
respectively.  From  these  figures  it  seems  apparent  that  as  these 
pigs  (excepting  the  2oo-pound  animals,  for  the  reason  mentioned 
immediately  above)  increased  in  age  and  in  weight  under  the  con- 
ditions of  a  widening  nutritive  ratio  of  the  rations,  there  was  an 
increase  in  the  quantities  of  food  nutrients  required  to  maintain 
their  live  weights.  The  loo-pound  pigs  apparently  required  for 
maintenance  2.5  percent  more  crude  protein,  19  percent  more  ni- 
trogen-free extract,  33.3  percent  more  crude  fiber,  30  percent  more 
ether  extract,  and  47  percent  more  metabolizable  energy  than  did 
the  5o-pound  pigs.  Further,  the  ration  which  maintained  the  150- 
pound  pigs  contained  5.7  percent  more  crude  protein,  25.5  percent 
more  carbohydrates,  37.5  percent  more  crude  fiber,  26.9  percent 
more  ether  extract,  and  37  percent  more  metabolizable  energy 
than  the  ration  which  maintained  the  loo-pound  pigs.  These  re- 
sults are  in  accord  with  those  of  other  investigators,  and  seem  to 
show,  in  general,  that  younger  pigs  require  less  for  maintenance 
per  loo  pounds  live  weight  than  do  older  ones.  However,  as 
Armsby  points  out,  this  may  be  due  to  the  fact  that  the  maintenance 
of  live  weight  in  a  young  animal  is  not  necessarily  synonymous 
with  the  maintenance  of  its  store  of  potential  energy.  It  is  pos- 
sible that  the  above-mentioned  increase  in  the  food  required 
for  maintenance  in  the  successive  periods  as  the  pigs  grew  older 
was  due  to  the  fact  that  the  nutritive  ratio  of  the  rations  for  the 
successive  periods  was  gradually' widened.  However,  further  in- 
vestigation will  be  necessary  in  order  to  determine  this  point. 

In  the  second  experiment,  one  Berkshire  pig  3  years  old,  weigh- 
ing approximately  510  pounds,  and  two  Poland-China  pigs,  one  il/2 
years  old,  weighing  approximately  375  pounds,  and  the  other,  i 
year  old,  weighing  310  pounds,  fed  upon  the  same  feeds,  but  in 
different  proportions,  were  maintained  on  0.14,  o.n,  and  o. n 
pound,  respectively,  of  digestible  crude  protein,  0.402,  0.404,  and 
0.401  pound  of  digestible  carbohydrates,  0.032  pound  of  digestible 
ether  extract  each,  and  about  1.766  therms  of  metabolizable  energy. 
The  maintenance  requirements  for  these  three  pigs  were  remarkably 


434  BULLETIN  No.  163  [June, 

similar  with  one  exception,  i.  e.,  the  crude  protein  for  the  Berkshire 
animal,  which  apparently  required  24.1  percent  more  protein  than 
either  of  the  other  two  animals.  There  were  so  many  variables  in 
this  experiment  that  may  be  of  significance  that  it  is  not  wise  to 
draw  definite  conclusions  from  the  results  until  further  experiments 
are  made  along  these  same  lines.  It  should  be  noted  also  that  the 
maintenance  requirements  obtained  in  this  experiment  are,  in  gen- 
eral, quite  similar  to  those  obtained  in  the  first  experiment,  espe- 
cially with  regard  to  the  5<>pound  pigs,  notwithstanding  the  fact 
that  the  breed,  age,  and  weight  of  the  pigs  were  different,  and  that 
the  kinds  and  quantities  of  the  feeds  and  the  nutritive  ratio  of  the 
rations  also  were  different  in  the  two  experiments. 

In  the  third  experiment,  of  two  Berkshire  barrows  of  the  same 
age  (16  months),  one  weighing  approximately  430  pounds  and  the 
other  330  pounds,  fed  upon  the  same  kinds  of  feeds  but  in  different 
proportions,  the  former  apparently  required  for  maintenance  0.078 
pound  of  protein,  0.228  pound  of  carbohydrates,  0.029  pound  of 
ether  extract,  and  about  1.117  therm  of  metabolizable  energy.  It 
seems  from  this  data  that  the  maintenance  requirement  of  the 
heavier  animal  was  somewhat  less  than  that  of  the  lighter  animal. 
The  difference,  however,  is  small  and  is  believed  by  the  writer  to 
be  within  the  limits  of  experimental  error  and  the  power  of  the 
pig  to  adapt  itself  to  the  conditions  supplied.  It  should  be  observed 
that  the  maintenance  requirements  obtained  in  this  experiment  were 
distinctly  lower  than  those  obtained  in  the  first  and  second  experi- 
ments. At  present  the  cause  of  this  difference  is  not  entirely  ap- 
parent from  the  experimental  data  available.  It  is  possible  that  one 
or  more  of  the  following  factors  was  instrumental  in  leading  to 
the  lower  results  found  in  the  last  experiment.  In  this  third  ex- 
periment the  pigs  had  been  maintained  for  a  longer  time  on  a  low 
nutritive  plane  before  the  final  maintenance  test  was  made  than  was 
the  case  in  the  two  former  experiments.  The  feeds  also  differed 
in  part  from  those  used  in  the  other  experiments,  i.  e.,  there  was 
more  variety,  and  pork  cracklings  were  used  in  this  last  experi- 
ment but  not  in  either  of  the  first  two.  Also,  as  previously  dis- 
cussed, relatively  more  protein  was  fed.  The  specific  effects  of  the 
feeds  may  have  played  some  part  in  yielding  the  variable  results 
obtained  in  the  experiments  here  reported. 

The  writer  believes,  judging  from  the  general  trend  of  the  re- 
sults of  this  series  of  experiments,  that  under  uniform  conditions 
the  actual  minimum  maintenance  requirement  per  100  pounds  live 
weight  is  fairly  constant  for  pigs  of  different  ages  and  breeds. 
This,  of  course,  would  not  hold  true  for  .pigs  in  different  degrees 
of  condition,  i.  e.,  the  fatter  pig  would  require  relatively  less  for 
maintenance  than  the  leaner  one.  This  entire  question  of  variability 


THE  MAINTENANCE  REQUIREMENT  OF  SWINE  435 

in  the  food  requirement  of  pigs  will  be  given  further    attention 
in  a  future  bulletin  from  this  department. 


CONCLUSIONS 

1.  The  results  of  the  experiments  here  reported  indicate  that 
the  maintenance  requirement  of  pigs  is  variable,  i.  e.,  one  and  the 
same  pig,  under  different  conditions,  may  maintain  its  live  weight 
on  distinctly  different  quantities  of  the  same  combination  of  feeds. 
This  variation  seems  to  be  due  to  the  plane  of  nutrition  upon  which 
the  pigs  have  been  maintained  previous  to  the  time  of  making  the 
maintenance  experiment. 

2.  The  results  also  indicate  that  the  maintenance  requirement 
of  pigs  which  previously  have  been  kept  on  a  low  nutritive  plane 
may  be  reduced  to  the  following  weights  of  nutrients  per   100 
pounds  live  weight :  digestible  crude  protein,  o.io  pound ;  digestible 
carbohydrates,  0.25  to  0.40  pound;  digestible  ether  extract,  0.03 
pound.     The  calculated  energy  requirement  for  the  above  main- 
tenance ration  on  the  same  basis  would  be  about  1.12  therms. 


The  author  wishes  to  acknowledge  the  valuable  advice  and  as- 
sistance received  from  Dr.  H.  S.  Grindley  and  Mr.  A.  D.  Em- 
mett,  of  this  department,  in  connection  with  the  experimental  and 
editorial  work  of  this  bulletin. 


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BULLETIN.  URBANA 
153-1651912-13 


30112019528428 


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